Wedge-shaped plenum chamber



May 17, 1966 T, MARINER WEDGE-SHAPED PLENUM CHAMBER Filed April l0, 1965 INVENTOR.

THOMAS MARINER 3,251,289 WEDGE-SHAPED PLENUM CHAMBER Thomas Mariner, Mount Joy, Pa., assigner to Armstrong Cork Company, Lancaster, Pa., a corporation of Pennsylvania Filed Apr. 10, 1963, Ser. No. 272,136 2 Claims. (Cl. 98-40) This invention relates to a building unit and more particularly to a building unit for the distribution of ventilating air to a room.

In the fabrication of building units to be used as a combination sound-absorbing ceiling, plenum chamber and air distribution system, consideration has been given to various integrated units which could be prefabricated. One unit is a tubular unit which is uniform in cross section and of a length suiicient to span a room. The ventilating air is fed in from one end of this unit from a suitable duct or plenum chamber and passes along the unit and through the openings in the bottom surface thereof into the room beneath. Di'lculty has been experienced with units of this type in obtaining a uniform distribution of air because as the air passes along the duct it loses velocity due to the loss of air passing through the openings in the bottom of the unit. This loss of velocity causes a loss of kinetic energy which in turn results in a build-up of potential energy thereby increasing the static pressure. Therefore it will be seen that there is a gradual build-up of static pressure from the entrance end of the unit to the far end with the greatest static pressure at the far end. This results in a unit in which the distribution of air through the porous or open bottom is not uniform but becomes greater as it progresses toward the end away from the entrance end. p

If the unit is of uniform cross section throughout its length, as the air passes through the openings in the bot tom the remaining air must expand to fill the duct thereby reducing the velocity. If the duct size diminishes proportional to the air loss, then the velocity remains constant.

The purpose of this invention is to provide a unit which will ensure uniformdistribution of the air along the entire length of the unit. This is accomplished by altering the -cross-sectional area of the tubular passage throughout at least a major portion of the distance from the entrance endtoward the opposite end from a maximum opening at the entrance end to a substantially smaller area with the decrease being proportional to the distance from the open end. This ensures a uniform static pressure as the air moves along and results in a uniform distribution of air through the bottom of the chamber.

The invention is particularly usable in those cases where prefabricated metal decking is used as an acoustical material. In these cases the Ventilating air is fed through ,one of the metal channels which has a perforated bottom surface and because the physical characteristics of the perforations have been selected for good sound absorption the air is not distributed uniformly throughout the length of the unit. In these instances it is particularly advantageous to place a baffle within the channel in such manner that the channel is largest at its entrance end and becomes smaller as it progresses toward the opposite end. In the preferred embodiment the passage is wedge-shaped. It desired, this baflie may have a sound-absorbing surface or it may be made of metal and have a pad of soundabsorbing material adhered thereto. In the case of making these units of berboard, the sloping baie will have a sound-absorbing surface so that the additional necessity for a sound-absorbing pad will not be required.

It is an object of this invention to provide a building unit which will serve as a conduit for conditioned air and ensure a substantially uniform distribution of air through the bottom surface of the conduit over an extended area.

lUnited States Patent O 3,251,289 Patented May 17, 1966 ICC In order that this invention may be more readily understood, it will be described in connection with the accompanying drawing in which FIGURE l shows a building unit of this invention, and

FIGURE 2 shows a piece of metal roof deck having this invention applied thereto.

Referring to FIGURE 1 there is shown a building unit having a bottom surface 2 which is preferably made of a sound-absorbent material such as wood ber or mineral ber which is porous enough to absorb sound or which has artiticial openings placed therein for the absorption of sound waves. Openings 3 are provided through this bottom layer 2 for the passage of Ventilating air from the interior of the unit through to the room beneath. The layer 2 serves as the ceiling of the room beneath. The unit has an open end 4 which is in communication with an air duct o1' a common plenum chamber positioned thereabove. The top 5 of the unit slopes from the open end of the unit toward the opposite end. This is a gradual slope ranging from about 1/2 or more at the open end to a substantially diminished cross-sectional area at the closed end. With this gradual slope it will be seen that the decrease in cross-sectional area `of the passage is proportional to the distance from the open end. With this arrangement when air is fed into the open end 4 under a slight pressure, the pressure is equalized as the air moves along forcing it uniformly through the entire length of the unit ensuring an equal distribution of air through the bottom 2 from the open end 4to the closed end 6. This is true regardless of the length of the unit, within reason of course. In most cases it will be from l0 to 12' in length so as to span the room in which it is installed.

The modification shown in FIGURE 2 is directed to a conventional corrugated steel deck 7 which has certain areas with perforations S designed for sound absorption but which may, with the aid of the invention, be used for the introduction of conditioned air into the room beneath. This deck is made of metal, and therefore the only way it absorbs sound is through exure which is negligible or by the `sound Waves passing through the openings provided for this purpose. In order to carry out the invention in connection with this embodiment, a

batlie 9 is placed in the channel of the corrugated deck- Y ing extending from the top of the channel at the entrance end to the bottom of the channel at the other end 11 forming a channel which is open at one end and closed at the other. This battle 9 may be of a fibrous nature which will absorb sound or it may be a metal or plastic member with a sound-absorbing medium adhered to the face thereof. The channel formed by the baffle 9 in the metal roof deck is designed so that the decrease in crosssectional area is proportional to the distance from the open end 10 so that the air continues to pass along the channel to the far end 11.

In those cases where the corrugated member of the deck forms a longitudinal passage which is of a shape otherV than rectangular, the bafe 9 must be contoured accordl ingly to ensure that the decrease in cross-sectional area is proportional to the distance from the open end.

It will be seen from the foregoing that I have developed a building unit which will ensure a uniform distribution of air through the bottom surface into a room beneath for air-conditioning purposes.

I claim: 1. A building unit for forming the ceiling of a room, said unit having a top, bottom and sides forming a chamber which is open at one end for the introduction of Ventilating air thereto, the bottom of said chamber being provided with openings for the conduction of Ventilating air therethrough to the room beneath, the top of the unit sloping from one end for a substantial portion of the entire length of the unit so as to form a chamber in which the decrease in cross-sectional area is proportional to the distance from the open end of the unit, the bottom surface of said unit being formed of a sound-absorbing material.

2. A building unit for forming the ceiling of a room, said unit having a top, bottom and sides forming a chamber which is open at one end for the introduction of ventilating air, the bottom of said chamber being provided with openings for the conduction of Ventilating air therethrough to the room beneath, the top of the unit sloping from one end for a substantial portion of the entire length of the unit so as to form a chamber in which the decrease in cross-sectional area is proportional to the distance from the open end of the unit, said unit being made at least partially of sound-absorbing material.

References Cited by the Examiner UNITED STATES PATENTS 10 WILLIAM F. ODEA, Primary Examiner.

ROBERT A. OLEARY, Examiner.

I. F. OCONNOR, Assistant Examiner. 

1. A BUILDING UNIT FOR FORMING THE CEILING OF A ROOM, SAID UNIT HAVING A TOP, BOTTOM AND SIDES FORMING A CHAMBER WHICH IS OPEN AT ONE END FOR THE INTRODUCTION OF VENTILATING AIR THERETO, THE BOTTOM OF SAID CHAMBER BEING PROVIDED WITH OPENINGS FOR THE CONDITION OF VENTILATING AIR THERETHROUGH TO THE ROOM BENEATH, THE TOP OF THE UNIT SLOPING FROM ONE END FOR A SUBSTANTIAL PORTION OF THE ENTIRE LENGTH OF THE UNIT SO AS TO FORM A CHAMBER IN WHICH THE DECREASE IN CROSS-SECTIONAL AREA IS PROPORTIONAL TO THE DISTANCE FROM THE OPEN END OF THE UNIT, THE BOTTOM SURFACE OF SAID UNIT BEING FORMED OF A SOUND-ABSORBING MATERIAL. 